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iron plates to 200—220°, and to lixiviate the product with water.
The acid is precipitated as the calcium salt, which is then decom-
posed with sulphuric acid.
G-lyoxylic and Grly collie Acids.—The process of electro-
lytic reduction has been applied successfully to a large number
of organic compounds, and has not only been found to have
definite practical advantages in many cases over other methods,
but, on account of the ease with which it may be controlled, has
elucidated the various stages in the mechanism of some of the
more complex changes. The reduction of nitro-compounds is
illustrated in Preps. 49 and 50. The reduction of organic acids,
ketones and carbonyl compounds generally has been developed
by Tafel and others, and in these cases it is found advantageous
to use a mercury or lead electrode. An essential feature of the
process is a clean metallic surface at the cathode and the absence
of foreign metallic impurities. The redaction of the carbonyl
group proceeds in three steps :
V                       V
>CO + 2li = C(OII) - C(OH)
>CO + 2l-I = >CHOII
>CO + 4ll = >CH2 + H,CX
Palmitic Acid.—This acid, together with stearicand oleic
acids, in the form of the glycerides, are the chief constituents of
fats. Palmitin (glyceride of palmitic acid) is also found in
certain vegetable oils like palm and olive oil. The acid occurs
also as the cetyl ester in spermaceti and as the myricyl ester
in bees-wax. It may be obtained from oleic acid by fusion
with potash,
Q8HW03 + 50 + 5KOH = daH.aO.jK + 2K2COa +4ILO.
In the analysis of oils and fats, where the quantity of fatty acid
is the  chief object of the determination,  it  is customary  to
hydrolyse the substance with a standard, solution of alcoholic
potash in place of aqueous potash, and to estimate the excess